设 x = secθ。则 dx = secθ*tanθ*dθ。那么,上式的定积分变换为:=∫secθ*tanθ*dθ/[secθ*√(sec²θ - 1)]=∫tanθ*dθ/tanθ=∫dθ=θ + C=arccos(1/x) + C
1.(3) 令 x = secu, 则 dx =secutanuduI = ∫ secutanudu/(secutanu) = ∫ du = u + C= arccos(1/x) + C